Supporting arm for developing machine



FIG. 1 is the perspective view of a supporting arm for developing machine showing my design;

FIG. 2 is a right side elevational view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a front elevational view thereof; and,

FIG. 7 is a rear elevational view thereof. 

The ornamental design for a supporting arm for a developing machine, as shown. 